<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="./vue.js"></script>
</head>
<body>
<div id="root"></div>
</body>
<script>
    const data={
        str:"abc"
    };
    const vm = new Vue({
       el: '#root',
       // data
        data: {
           str:"1234"
        }
    })
    // console.log(vm.$data); //abc
    // console.log(vm.str); //1234
</script>
</html>